A wireless ad hoc network refers to a network with no base structure, that is autonomously configured by nodes thereof. That is, the wireless ad hoc network is a network that does not require a base network device such as a base station or an access point, for network configuration and maintenance.
It is important to configure a routing path consuming minimum power in a wireless ad hoc network.
An optimal transmission path configuration method for raising energy efficiency in the wireless ad hoc network includes transmission techniques of multiple input multiple output (MIMO) and virtual MIMO (V-MIMO). Among these, a variety of MIMO transmission techniques has been developed due to high bandwidth efficiency of a MIMO transmission scheme. However, since circuit construction of a transmitter and a receiver for MIMO transmission becomes complicated and energy consumed in a circuit of the transmitter and the receiver increases, the MIMO transmission techniques have a difficulty in being used in the wireless ad hoc network. Further, installation of a plurality of antennas to a small sensor is also an obstacle to implementation of MIMO transmission techniques. Due to such problems, a V-MIMO transmission technique using a virtual antenna array has been proposed as a solution for applying MIMO techniques to an ad hoc network. While the wireless ad hoc network to which V-MIMO is applied has an advantage of multiplexing gain, energy is additionally consumed and transmission delay occurs, for cooperation between sensors participating in transmission. Accordingly, in the case where a data transmission distance is short, the V-MIMO transmission technique is inefficient in terms of energy and delay time.
Meanwhile, all of ad-hoc on-demand distance vector (AODV), dynamic source routing (DSR), and dynamic MANET on-demand (DYMO) are on-demand routing algorithms for the wireless ad hoc network. AODV is based on destination-sequenced distance-vector routing (DSDV) which is a table-driven algorithm based on a Bellman-Ford algorithm. If there are no valid paths when a source node starts transmission to a destination node, this routing protocol operates to form a path in such a manner that the source node searches for a path from neighboring nodes and middle nodes by broadcasting a route request (RREQ) message and nodes capable of forming the path transmit a route reply (RREP) message to the source node.
DSR maintains a routing path by maintaining and updating a path cache known to a mobile node. If there is a valid path up to a destination node when a source node starts transmission, this routing protocol operates to form a path in such a manner that the source node stores the path cache and transmits packets. If there are no paths, the source node performs path search by broadcasting an RREQ packet. Upon encountering a node including a valid path cache, the destination node transmits an RREP packet.
DYMO is a wireless ad hoc on-demand protocol for forming a path through an RREQ message and an RREP message, similarly to AODV and DSR. DYMO is a routing protocol developed after AODV and more easily implemented than AODV while maintaining advantages of AODV.
In the above protocols, only one equal transmission scheme is used among single input single output (SISO), virtual SISO (V-SISO), virtual multiple input single output (V-MISO), and V-MIMO. Accordingly, energy efficiency is reduced in every transmission distance of one hop.